The invention relates to cascade drive systems which are commonly used in processes that deal with continuous lengths of material such as film, wire, paper, fabric, etc. In particular, it relates to a method of creating a cascade drive system using hydraulic components which are arranged in a series flow circuit in such a way that adjustment of the speed of any output shaft proportionately and synchronously adjusts the speed of all subsequent output shafts in the system.
Present methods of achieving such cascade drive systems are by use of electronic control of DC motors in what are called tach-follower systems, and by placing mechanical speed variators between adjacent stages of a drive system. However, these methods create certain distinct disadvantages. In this regard, an electronic drive system involves considerable cost, bulky size, and the necessity to incorporate regenerative drives on stages that handle over-hauling loads. That is, loads that actually add power back to the drive system because of energy received from the processed material. Although the cost of mechanical speed variator drive systems is comparatively low, speed regulation achieved is relatively poor. Also, mechanical speed variators place stringent requirements on relative location of the various stages of the drive system, since all power must be transferred by chains, belts, gears, or the like.
Hence, for efficiency and adaptability, a cascade drive system is needed which is low in cost, reasonable in size, flexible in arrangement, and can transmit relatively large quantities of power with good speed and ratio regulation. It is an object of this invention to provide a cascade drive system for efficiently regulating speeds and speed ratios throughout the system.
It is another object to provide a cascade drive system capable of regeneration of power from over-hauling loads.
It is a further object to provide a cascade drive system with a flexible spatial relationship between the various stages of the drive system.
It is yet another object to provide a cascade drive system at a fractional cost of an equivalent electronic system, while maintaining approximately equal control features.
Still another object is to provide a cascade drive system with relatively small components that are capable of transmitting large quantities of power.